Urethan-anesthetized rats were used to identify effective stimuli for the release of the
peptides arginine vasopressin (AVP) and
oxytocin into the ventral septal area (VSA) of the brain. Febrile responses to intracerebroventricular injection of
prostaglandin E1 (
PGE1) were observed in rats whose body temperatures were maintained at 35, 37, or 39 degrees C. Microinjection of the AVP antagonist
d(CH2)5Tyr(Me)AVP into the VSA enhanced
fever only when
PGE1 administration was associated with a significant rise in body temperature. Passive elevation ("artificial
fever") or reduction of body temperature in the absence of a
PGE1 stimulus was not affected by the antagonist. Push-pull perfusion of the VSA and the dorsal hippocampus, followed by radioimmunoassay of perfusates for AVP and
oxytocin, revealed enhanced release into the VSA of AVP only when
PGE1 administration was followed by a rise in body temperature.
Oxytocin was released whenever body temperature was raised.
Peptide concentrations in simultaneous perfusates of dorsal hippocampus did not change in response to
PGE1 administration or to passive elevation of body temperature. We conclude that AVP is released into the VSA, but not the dorsal hippocampus, of the rat during a
fever induced by
PGE1.
Oxytocin is released into the VSA, but not the hippocampus, when temperature is elevated.